As is known in the art, Si CMOS VLSI integration capability is passing the one-billion transistors level. As is also known in the art, some applications require that analog, RF or electro-optical devices also be formed on the same substrate as the CMOS devices. These analog, RF or electro-optical devices are typically III-V devices. One technique described to integrate the CMOS devices and the III-V devices uses a seed layer of Ge, as described in U.S. Patent Application publication No. 2008/0149915 A1 published Jun. 26, 2008, see also U.S. Pat. Nos. 7,374,106; 7,286,726; 7,057,256; 6,930,82; 5,767,539, 6,154,475, 7,321,713, and 7,057,256. See also, “Fabrication of silicon on lattice-engineered substrate (SOLES) as a platform for monolithic integration of CMOS and optoelectronic devices”, by Dohrman et al., published in Materials Science and Engineering B 135 (2006) 235-237. See also “Direct Growth of III-V Devices on Silicon”, by Herrick et al., published in Material Research Society Symposium Proceedings, Volume 1068, Materials Research Society (1068-C02-10).
As is also known in the art, high temperature process techniques are used to form small geometry, Cu on TaN or TiN, electrical contacts to the CMOS devices, while on the other hand, III-V electrical contacts are typically TiPtAu or TiAu and are fabricated using lift off techniques.
The inventors have recognized that the use of the TiPtAu or TiAu lift off techniques limits the circuit density and is also incompatible with the well established Si CMOS VLSI copper based interconnect process. This invention solves the problem of interconnects between the heterogeneously integrated III-V devices with the Si CMOS VLSI copper based metal interconnect process at the very first level of metal interconnect step. This invention describes a metallization scheme for heterogeneous integration of III-V devices with Si CMOS which is fully compatible with CMOS VLSI metal interconnect process.
In accordance with the present invention, a semiconductor structure is provided having: a substrate; a seed layer over the substrate; a silicon layer disposed on the seed layer; a transistor device in the silicon layer; a III-V device disposed on the seed layer; and a plurality of electrical contacts, each one of the electrical contacts having a layer of TiN or TaN and a layer of metal on the layer of TaN or TiN, one of the electrical contacts being electrically connected to the Si CMOS transistor and another one of the electrical contacts being electrically connected to the III-V device.
In one embodiment, the metal is copper or aluminum.
With such an arrangement, the problem of interconnects between the heterogeneously integrated III-V devices with the Si CMOS VLSI copper or aluminum based metal interconnect process at the very first level of metal interconnect step is solved. The arrangement is fully compatible with CMOS VLSI metal interconnect process. The arrangement uses advanced thin film technology available today, such as Atomic Layer Deposition (ALD) method to provide a fully CMOS VLSI process compatible metal interconnects method by the use of ALD deposited TiN and/or TaN to contact the source, drain, and gate of III-V FET or emitter, base, and collector of III-V HBT to prevent the interdiffusion between these contacts and the copper (Cu) or aluminum (Al) based SI CMOS VLSI interconnects. Furthermore, the arrangement provides copper or aluminum based low resistance and inductance access to the terminals of III-V based devices in a heterogeneously integrated III-V device on a Si substrate. As mentioned previously, the arrangement is fully compatible with Si CMOS VLSI metal interconnects process.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.